Balance Sheet Details (Accounts Receivable and Inventory) (Details) (USD $) In Millions, unless otherwise specified	Dec. 30, 2012	Dec. 25, 2011	Dec. 26, 2010	Dec. 27, 2009
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents - Amortized Cost Basis	$ 49.0	$ 69.6	$ 10.8	$ 9.9
Cash and cash equivalents - Level 1 Fair Value Basis	49.0	69.6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current accounts receivable, gross	273.3	247.3
Allowance for doubtful accounts	(1.4)	(2.0)
Total current accounts receivable, net	271.9	245.3
Total accounts receivable, net	272.2	245.6
Retainages receivable	3.5	3.9
Inventory, Net of Allowances, Customer Advances and Progress Billings [Abstract]
Raw materials	48.4	43.3
Work in process	36.5	25.7
Finished goods	7.3	6.9
Supplies and other	2.2	4.0
Subtotal inventoried costs	94.4	79.9
Less customer advances and progress payments	(0.1)	(3.3)
Total inventoried costs	94.3	76.6
Billed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current accounts receivable, gross	137.9	128.7
Unbilled
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current accounts receivable, gross	135.4	118.6
Unbilled, long-term (included in other assets)	0.3	0.3
U.S. Government
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable, net	64.0	84.5
U.S. Government | Billed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable, net	24.6	41.2
U.S. Government | Unbilled
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable, net	$ 39.4	$ 43.3